At first the good news: The Excel
ISOWEEKNUM function corresponds to the MySQL
WEEKOFYEAR which is WEEK(date,3). So determining ISO week numbers is possible.
But all other WEEK modes are simply crap because the definition of the first week in year does not fit any logic used elsewhere. For example, take the simplest mode having Sunday as the first day of the week and the first week of the year is the week, the first day of the year falls in. This is what Excel
s WEEKNUM function returns with Return_type
1 or omitted. This should be MySQL
s WEEK
in modus 0 (0-53) or 2 (1-53). But what the heck?
SELECT WEEK('2008-01-01',0);
-> 0
SELECT WEEK('2008-01-01',2);
-> 52
So MySQL
tells us, Tuesday, 2008-01-01, is in week 52 of 2007?
Really? Why?
Because the rule "Week 1 is the first week … with a Sunday in this year" is not fulfilled by MySQL
. Instead it seems for MySQL
the first week starts with the first Sunday in this year.
So except of the ISO week numbers, all other week numbers from MySQL
are wrong. One could think: Let us take modus 0 and simply add 1 to the result. But that fails in 2012. Because there 2012-01-01 is Sunday and there MySQL
gives week number 1 in modus 0 as well as in modus 2.
Examples:
Excel:
Date WEEKNUM ISOWEEKNUM
2008-01-01 1 1
2008-02-01 5 5
2008-02-03 6 5
2008-02-04 6 6
2008-12-31 53 1
2009-01-01 1 1
2009-02-01 6 5
2009-12-31 53 53
2012-01-01 1 52
2012-02-01 5 5
2012-12-31 53 1
2016-01-01 1 53
2016-02-01 6 5
2016-12-31 53 52
MySQL:
drop table if exists tmp;
create table tmp (d date);
insert into tmp (d) values
('2008-01-01'),
('2008-02-01'),
('2008-02-03'),
('2008-02-04'),
('2008-12-31'),
('2009-01-01'),
('2009-02-01'),
('2009-12-31'),
('2012-01-01'),
('2012-02-01'),
('2012-12-31'),
('2016-01-01'),
('2016-02-01'),
('2016-12-31');
select d as 'Date', week(d,0), week(d,3) from tmp;
Result:
Date week(d,0) week(d,3)
2008-01-01 0 1
2008-02-01 4 5
2008-02-03 5 5
2008-02-04 5 6
2008-12-31 52 1
2009-01-01 0 1
2009-02-01 5 5
2009-12-31 52 53
2012-01-01 1 52
2012-02-01 5 5
2012-12-31 53 1
2016-01-01 0 53
2016-02-01 5 5
2016-12-31 52 52